A more complete understanding of the molecular mechanisms that support milk synthesis are needed to develop strategies to efficiently and sustainably meet the growing global demand for dairy products. With the postulate that coding gene transcript abundance reflects relative importance in supporting milk synthesis, we analyzed the global transcriptome of early lactation cows across magnitudes of normalized RNA-seq read counts. Total RNA was isolated from milk samples collected from early lactation cows (n=6) following two treatment periods of post-ruminal lysine infusion of 0 or 63 g/d. Twelve libraries were prepared and sequenced on an Illumina NovaSeq6000 platform using paired end reads. Normalized read counts were averaged across both treatments, because EBseq analysis found no significant effect of lysine infusion. Approximately 10% of the total reads corresponded to 12,730 protein coding transcripts with a normalized read count mean ≥5. For functional annotation analysis, the protein coding transcripts were divided into nine categories by magnitude of reads. The 13 most abundant transcripts (≥50K reads) accounted for 67% of the 23M coding reads, and included casein and whey proteins, regulators of fat synthesis and secretion, a ubiquitinating protein, and a tRNA transporter. Mammalian target of Rapamycin (mTOR), JAK/STAT, peroxisome proliferator-activated receptor alpha (PPARα), and ubiquitin proteasome pathways were enriched with normalized reads ≥100 counts. Genes with ≤100 reads regulated tissue homeostasis and immune response. Enrichment in ontologies that reflect maintenance of translation, protein turnover, and amino acid recycling indicated that proteostatic mechanisms are central to supporting mammary function and primary milk component synthesis.

中文翻译：

---

乳腺转录组揭示了早期泌乳母牛的细胞维持和蛋白质更新支持牛奶合成。

需要更全面地了解支持牛奶合成的分子机制，以开发有效，可持续地满足全球对乳制品不断增长的需求的策略。假设编码基因转录本的丰度反映了在支持牛奶合成方面的相对重要性，我们分析了标准化母牛RNA序列读数计数范围内早期泌乳母牛的整体转录组。在瘤胃后赖氨酸输注两个治疗期0或63 g / d后，从早期泌乳母牛（n = 6）收集的牛奶样品中分离总RNA。制备了十二个文库，并使用配对末端读取在Illumina NovaSeq6000平台上测序。两种治疗方法的标准化读数均取平均值，因为EBseq分析未发现赖氨酸输注的明显作用。总读数的大约10％对应于12,730个蛋白编码的转录本，标准化的读数计数平均值≥5。为了进行功能注释分析，将蛋白质编码转录本按阅读强度分为九类。13种最丰富的转录本（≥50K读本）占23M编码读本的67％，其中包括酪蛋白和乳清蛋白，脂肪合成和分泌的调节剂，泛素蛋白和tRNA转运蛋白。雷帕霉素（mTOR），JAK / STAT，过氧化物酶体增殖物激活的受体α（PPARα）和泛素蛋白酶体途径的哺乳动物靶标具有≥100计数的标准化读数。≤100的基因可读取调节的组织稳态和免疫反应。丰富的本体反映了翻译的维持，蛋白质更新，